Camless regulator for grading devices



Nov. 21, 1950 C. C. THOMAS CAMLESS REGULATOR FOR GRADING DEVICES FiledJune 19, 1948 INDICATED THICKNESS 2 Sheets-Sheet l BLANK THICKNESS EI'E.E.

PER FEGT TRAVEL UNREGULATED FOR COSINE ERROR UNREGULATED FOR LINEAR TRAVEL ERROR AND INCREASING SPRING LOADING UNREGULATED FOR- LINEAR TRAVELERROR TTIV mar CHARLES C. THOMAS Nov. 21, 1950 c. c. THOMAS CAMLESSREGULATOR FOR GRADING DEVICES Filed June 19, 19 18 2 Sheets-Sheet 2 Invmnr 6H4 RL E5 0. moms Gil" i113 Patented Nov. 21, 1950 CAMLESS REGULATORFOR GRADING DEVICES Charles C. Thomas, Medford, Mass., assignor to NorthAmerican Research Corporation, Cambridge, Mass., a corporation ofMassachusetts Application June 19, 1948, Serial No. 34,031

Claims. 1

This invention relates to grading machines used in the shoe industry,particularly to a mechan'sm for regulatingthe action of the Nichols typegrader, disclosed in Pat. No. 1,130,321, which is used for measuring thethickness of soles, heel lifts, counters, taps, and similar leatherblanks.

A grading machine of the type to which this invention relates employs asthe detecting element a pair of continuously driven rolls. The verticalposition of the upper roll is fixed. The lower roll is movable up anddown and is springpressed toward the upper roll. The motion of the lowerroll is communicated through a yoke and a pair of connecting rods to atransmission lever which may operate various mechanisms for indicating,skiving, sorting, marking, and distributing the leather blanks inaccordance with the measured thickness. The blanks may be fed to therolls manually or automatically. After passing through the detectorrolls the blanks pass to a moving chain which carries them on to theskiving, distributing, or other mezhanism. At the start of the gradingoperation, the lower detector roll and transmission lever are both freeto drop downward and admit the blank. A short time after the leading endof the blank has entered a ratchet mechanism locks the transmissionlever against further downward movement. Thereafter during the passageof the blank through the rolls, the lower roll is free to move in bothdirections but only its upward movement is transmitted to the m chanismswhich are to perform the further operations so that the operatingmechanism, which may be a skiving knife, a stamping device, or anindicator, for example, is set in accordance with the minimum measuredthickness of the blank.

Grading machines constructed substantially in accordance with theNichols patent referred to above are in general use in the shoeindustry, and give satisfactory measurement to the nearest half iron.Where greater accuracy is required, however, provision must be made forregulating the response of the indicating or operating mechanism to themotion of the detector rolls. The function of such a regulator istwo-fold, to modify the grading response to meet particular operationalrequirements, and to compensate for various sources of error.

The efficiency of operaticns on certain types of leather may often beimproved by setting the machine so as to depart somewhat from perfectgrading. In skiving soles of widely varying thickness, for example, itmay be advantageous to take a light out from very thin soles and adeeper cut from thick soles. Another example of situatlon in which itmay be expedient to modify the grading response is in grading flexibleinner soles. In this case the blanks must be graded from a point asclose as possible to the leading known as the cosine error.

sole results in overgrading, that is the indi-,

cated thickness is greater than the actual minimum thickness of theblank. This effect can be compensated for by introducing a certainamount of losing travel, that, is, by setting the transmission mechanismso that the indicated thickness is less than the roll separation. An-

other error, which may be appreciable results from the compressibilityof the leather. A certain amount of spring pressure is required tomaintain positive contact between the detector rolls and the blank. Theblank is, therefore, compressed as it passes through the detector rollsand it is apparent that a machine calibrated by steel gauge blocks willunde grade on leather, that is, the indicated thickness will be smallerthan the .actual thickness of the blank so that considerable unnecessarywaste is incurred if the blanks'are skived to the indicated thickness.This efiect is known as the linear travel error. Since the percentageerror is constant for constant pressure, the magnitude of errorincreases in proportion to thickness or" the blank. The effect ofcompressibility is aggravated by the increase in the spring loading onthe lower roll as it moves downward. This type of error cannot beallowed for in the initial calibration of the machine, be-

cause dilferent types of leathers vary widely in firmness. Anothereffect ordinarily negligible, is

In the original machine the motion of the lower detector roll iscommunicated to the transmission lever by a pair of connecting rodswhich act on the lever at a fixed distance frcm the shaft which servesas the fulcrum. As the lever moves away from the horizontal, thehorizontal distance between the shaft and the connecting rods isdecreased, so that the mechanical advantage of the system is increased,giving rise to overgrading. Dimensional variations within normalmanufacturing tolerances may also give rise to appreciable errors,unless some provision is made for adjusting the machine after it isassemb'ed.

A regulating device for the Nichols type grader is described in PatentNo. 2,180,591 to James W. Johnston. According to the Johnston patent apair of slides are mounted in guideways on the underside of thetransmission lever and provide a movable-junction point between theconnecting rods and the transmission lever. The slides terminate in armswhich ride on adjustable cams. As the lever moves away from thehorizontal, the cams drive the slides so as to shift the point ofapplication of the roll motion to the lever. As set forth in theJohnston patent, this device was described as a means to compensate forthe cosine error, but it is primarily useful for altering the mechanicaladvantage of the transmission system for the purpose discussed above.The Johnston regulator has considerably improved the accuracy andflexibility of the Nichols type grader, but is subject to someobjections. For example, the regulator increases the friction of thetransmission mechanisms. The added friction interferes with the returnto the startgrading position aggravating the aforementioned dimculty ingrading flexible inner soles. Another disadvantage is that randomvariations are introduced into the grading response by backlash and lostmotion between the moving parts of the regulator mechanism. Dirt andwear between the cams and the follower arms also cause difiiculty.Furthermore, the range of adjustment is limited in the Johnston deviceso that two different models, having different slide lengths, arerequired to meet the demands of the shoe industry.

The object of this invention is to provide a regulating device which isadaptable to grading machines of the Nichols and similar types; whichcompensates more accurately and fully than regulators now in use, forthe main sources of error in grading; which has a Wide range ofadjustments so that one type of regulator satisfies present commercialrequirements; which adds no moving parts to the transmission mechanism;which is readily adjusted and maintains its setting accurately; which issimple in construction; and, which is impervious to wear and dirt.

Other advantages and novel features of the device will be apparent fromthe following description, with reference to the drawings, on which:

Fig. 1 is a partial cross-section through a. grading machine, with theregulator installed, in the plane of one of the connecting rods, partsof the machine being broken away or schematically indicated forconvenience;

Fig. 2 is a graph showing the effect of various errors and adjustmentson the grading response;

Fig. 3 is a partial plan view of the transmission lever with theregulator attached; and

Fig. 4 is a front elevation of the parts shown in Fig. 3.

The operation of a machine of this type can be understood insofar as isnecessary for an explanation of this invention by reference to Fig. 1.The blank to be graded is fed either manually or automatically fromtable 5 into detector rolls 6 and I. Roll I is fixed to shaft 8, whichis journalled in a fixed bearing in the frame it, of the machine, and iscontinuously driven. Lower roll ii is fixed to shaft 9 which isjournalled at each end in boxes l2. The boxes slide in vertical guideways It. The lower roll is springpressed upward by means not shown.Rotary motion is imparted from the upper roll to the lower by Wringergears I5 and H fixed to shafts 9 and 8, respectively. A yoke l5 followsboxes 12,. A pair of connecting rods ll are journalled at their upperends on pins l8 which are slidable along their longitudinal axes in yokeIt and are secured by cotter pins I9. This arrangement permitshorizontal motion between the yoke and the connecting rods. Theconnecting rods project through openings 32 in the cross-piece 30 oftransmission lever 23 and are threaded on their lower ends to receiveball nuts 2| and lock nuts 22. Seats 3! in slides 38 form, with ballnuts 2|, separable universal joints between the connecting rods and thecross-piece 30 of transmission lever 23. A spring 4| tends to maintainseparation between yoke l5 and lever 23 to the extent permitted by ballnut 2|. Lever 23 is journalled on a shaft 24 fixed in the frame of themachine, and carries gear sector 25 on its free end. Gear sector 25engages with gear sector 26 which is fixed to a shaft 46, journalled inthe frame of the machine. A ratchet 45 is also fixed to shaft 46. Themotion of the shaft is transmitted through suitable linkages to anydesired skiving, indicating, or other mechanism (not shown). During thegrading operation, that is during the passage of a blank through rolls,pawl 28 engages ratchet 45 and locks lever 23 against downward motion.Upward motion of roll 6 will then be transmitted through yoke l5 andconnecting rods IT, to lever 23, but subsequent downward motion of therolls serves only to compress spring 4 l It is apparent from theforegoing description that the position of lever 23, and consequentlythe setting imparted to the indicating or other mechanism by therotation of shaft 46, at the end of the grading operation, willcorrespond to the minimum thickness encountered by the rolls 6 and I.Just before the blank leaves the rolls, shaft lfi is locked (by meansnot shown) until the desired further operations have been performed onthe blank. The blank passes onto toothed chain I6 which carries it tothe skiving, marking or other operating mechanism. When the machine isready to admit the next blank, pawl 28 is momentarily released so lever23 may drop down with roll 6 when the blank enters the rolls. Shortlyafter the blank enters, pawl 28 is dropped into engagement with ratchet45, locking lever 23 against subsequent downward motion. A more detailedexplanation of the operation of a grading machine of this type will befound in the Nichols patent previously referred to. Further descriptionis omitted herein as not essential to an understanding of thisinvention.

Fig. 2 illustrates the effect of some of the errors previously mentionedherein. Assuming an incompressible blank and a linearly calibratedindicator, for example, a dial marked in equal angular increment tocorrespond to equal increments of motion of the lower roll, if themotion transmitted to the indicator were exactly proportionate to themotion of the roll, the plot of indicated thickness against blankthickness would be a line with a forty-five degree slope, hererepresented by the perfect travel line. With the transmission mechanismshown, however, the radial distance from shaft 24 to rods I1 is fixed,so that, as lever 23 moves away from the horizontal, the horizontaldistance between shaft 24 and the point of application of the verticalforce transmitted through rods I I becomes less and, therefore, themotion of gear sector 25 and consequently the indicator motion for agiven roll travel becomes greater. The result of this departure fromtrue proportionate transmission is illustrated by the curve designatedunregulated for cosine error. The curve is here shown exaggerated forthe purpose of illustration. Over the limited range of rotation throughwhich lever 23 normally moves, the cosine error is relatively small andmay be closely approximated by a straight line. If the material of theblank to be measured is compressible, as is t -e actual case, theseparation of the roll will correspond not to the actual thickness ofthe blank, but to a certain substantially constant percentage of thethickness, the reduction in thickness for a given pressure beingapproximately proportionate to the thickness of the piece. Thecorresponding curve of indicated, against actual, thickness formechanism set by means of steel gauge blocks to give perfect travel, isillustrated by the curve designated unregulated for linear travel error.In the actual case, the pressure on the blanks is not constant, butincreases in proportion to roll travel according to the Well-knownformula for spring pressure. When operating on compressible blanks,therefore, the grading curve of a mechanism set for perfect travel onsteel is approximately parabolic in form as shown by the curvedesignated unregulated for linear travel error and increasingspring-loading.- For the range of thickness which a machine of this typeis expected to measure, however, this curve, like the cosine error curvecan be closely approximated by a straight line. The effect of curls inthe leather is, of course, largely unpredictable, but results inovergrading. The proper amount of losing travel to account for curls canbest be determined by a few experimental measurements on the particulartype of leather which is to be graded.

From a study of Fig. 2, it is apparent that the normal sources of errorin grading can be compensated for, over the operating range by changingthe slope of the grading curve, that is, by altering the mechanicaladvantage of the transmission system so that the indicator readingcorresponds to a value somewhat more or less than actual roll travel.Figs. 1 3 and 4, illustrate regulating mechanism suitableforaccomplishing this result. The cross-piece 39 of lever 23 is built upon the underside, as seen in Fig. 4. The sides of the thickened sectionmay be machined to form guides ll for slides 38, or guides for theslides may be provided in any other well-known manner. In the examplehere shown, slides 33 are retained by plates 48, attached to lever 23 byscrews &9. The slides carry seats st for ball nuts 2!, and are joinedtogether at the front by yoke M. A threaded stud 33 is welded to yokeid. This stud engages in adjusting screw 35 which is recessed andtapped. The screw 35 projects through back plate and is retained by nuts50 and 5!. A curled hand knob H is provided on the outer end of screw35. By turning screw 3%, slides 38 may be moved in the longitudinaldirection of lever 23, so altering the length of the lever arm betweenshaft 2 and rods ll. Since this arm is much shorter than the distancefrom shaft 22. to gear sector 25, a relatively small travel of slides 38provides a considerable range of adjustment for the mechanical advantageof the transmission system.- The corresponding curve of indicated,against actual, thickness may thus be made very close to the perfecttravel curve for blanks of a reasonably uniform firmness, or

any desired over-or-under-grading may be introduced. To facilitatesetting a suitably calibrated indexing rod 52 may be attached to yoke M.The rod 52 projects through a hole in plate 36. A nut 35 having a handle53 is provided for locking screw 36 at the desired setting so thatduring the grading operation no motion takes 3? e between the regulatorslides and the transicn lever. The appreciable friction introduced byother regulators, for example the Johnston type, is thus entirelyeliminated in this device.

Since certain changes may be made in the above-described article anddifferent embodiments of the invention could be made without departingfrom the scope thereof, it is intended that all matter contained in theabove description or shown in the accompanying drawing shall beinterpreted as illustrative only and not in a limiting sense.

What is claimed is:

1. In a grading machine having a movable detector roll and a lever fortransmitting the motion of the roll to other mechanisms; a yokeconnected to saidroll; a pair of pins axially slidable in said yoke; apair of connecting rods, the upper ends of which are journalled on saidpins; clearance holes in said yoke about said rods; ball nuts on theends of said rods; slides mounted on the underside of said lever; seatsfor said nuts on the underside of. said slides; means for shifting saidslides longitudinally on said lever; and a mechanical lock for securingaid slides in a desired position on said lever.

2. Apparatus according to claim 1 wherein said shifting means comprises:a yoke connecting said slides together; a threaded stud attached to saidyoke; a back plate attached to said lever; and an adjusting knobjournalled in said back plate and internally threaded to receive saidstud.

3. Apparatus according to claim 2 wherein said knob is threaded on itsshank and retained by a nut on the inner side of said plate, and theposition of said slides is locked by means of a nut mounted on the shankof. said knob on the outer side of said plate.

4. Apparatus according to claim 2 having an indicating rod attached tosaid yoke and pro- 0 jecting through a holein said plate.

5. In a grading machine having a movable detector roll and a lever fortransmitting the motion of the roll to other mechanisms; a pair ofslides spaced apart and mounted on said lever adjustably in itslongitudinal direction; a pair of correspondingly spaced connecting rodsconnected by universal joints to said slides; a connection between saidroll and said rods slidable in said longitudinal direction; and amechanical lock for securing said slides in a desired position on saidlever.

CHARLES C. THOMAS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,130,321 Nichols Mar. 2, 19151,405,926 Lauer Feb. '7, 1922 2,186,591 Johnston Nov. 21, 1939 2,264,254Brandt Nov. 25, 1941 FOREIGN PATENTS Number Country Date 163,692 GreatBritain Feb. 16, 1922

